If the MySQL root user account has a
password, you need to invoke mysqladmin
with the -p option and enter the password
when prompted.

Before upgrading to MySQL 5.0 from a version
previous to 4.1.5, or from a version of MySQL installed from a
Zip archive to a version of MySQL installed with the MySQL
Installation Wizard, you must first manually remove the
previous installation and MySQL service (if the server is
installed as a service).

To remove the MySQL service, use the following command:

shell> C:\mysql\bin\mysqld --remove

If you do not remove the existing
service, the MySQL Installation Wizard may fail to properly
install the new MySQL service.

If you are installing MySQL from a Zip archive, extract the
archive. You may either overwrite your existing MySQL
installation (usually located at
C:\mysql), or install it into a different
directory, such as C:\mysql5. Overwriting
the existing installation is recommended.